Charlotte -LRB- CNN -RRB- -- Four years later , consider the role reversal : As he closes his convention , Barack Obama 's greatest challenge is to make the case against change .

Yet he ca n't ask the American people to simply stay the course .

The challenge , both daunting and delicate , is to make the case that his first-term policies were correct but that the second-term results will be dramatically different .

Veteran Democratic pollster Peter Hart says the president 's challenge is to provide a clear and credible answer to this : `` Why will you be better off in the second term ? ''

And Hart argues that the stakes , already high , are higher still now because of the strong prime-time performances of first lady Michelle Obama and former President Bill Clinton .

`` This convention is now a home run derby , '' Hart said .

Four years ago in Denver , Sen. Barack Obama sold himself as the candidate of hope and change , presenting himself as a different brand of politician , someone who would change Washington -- and the economy -- for the better .

Obama to speak after forceful Clinton endorsement

But if Washington has changed at all , it is for the worse . And while both sides can find statistics that support their arguments on the state of the economy , it is clear that many Americans at best feel they are treading water .

So the tone is very different in Charlotte than in Denver . So is the targeting . Four years ago , the goal was to expand the map , and the Obama campaign ultimately succeeded .

This year , the path to 270 Electoral College votes and victory is less certain , though the president does have more viable options than does GOP nominee Mitt Romney .

Still , because of the changed climate , the Obama acceptance speech will close a Democratic convention that for the most part has been a giant get-out-the-vote rally , speakers chosen because of their appeal to specific constituencies -LRB- African-Americans , Latinos , suburban women , gays and lesbians -RRB- or major battleground states .

The most sustained appeal to undecided or independent voters was Wednesday 's prime-time dissertation by Clinton .

Speaking to supporters Thursday morning , the president talked broadly about his test of convention success .

`` Hopefully , at the end of this convention , people will say we accomplished what we needed to and delivered our vision for the country and offered a clear contrast to what people saw in Tampa , '' the president said .

Obama readies two-term pitch

While Charlotte has had plenty of contrast with the GOP convention in Tampa , there has been virtually no specific talk of the president 's policy goals for the next four years . Will he , like Romney , offer a specific jobs target ? Will he offer a new deficit reduction goal ? Venture into goals or timetables for immigration reform ?

How the president packages his pitch also could be defining .

For Ronald Reagan , the second term was wrapped as `` Morning in America . '' Clinton 's 1996 bid for a second term was sold as his `` Bridge to the 21st Century . ''

Thursday night , Obama 's challenge is to sell his road map .

And beyond the need to lay out a second-term policy agenda , some other Obama challenges are obvious .

Voters , albeit by a narrow margin , view Romney as better able to manage the economy . And while Obama leads when voters are asked which candidate best understands the middle class , the latest CNN/ORC International polling showed that Romney significantly narrowed that gap as a result of the Republican convention .

The president 's top political advisers see discouragement as their greatest potential enemy . Proof of this is in a look at recent national polling : The president 's numbers among registered voters are stronger than his numbers among likely voters , meaning a fair share of potential Obama voters are n't as engaged or interested this time around .

First lady seeks to reignite flame for president

Again , that is the strategy behind the convention agenda : careful targeting of the different pieces of the Obama 2008 coalition .

But for all the help he is getting from his friends , it is up to Obama himself to close the deal .

Now , the role of one speech should not be overstated . Just hours after the convention closes , the government will release August jobs data -- and that data could significantly shape morning-after reflections on the president 's big moment .

Plus , there are two months of campaigning and three presidential debates ahead , so this is n't his last chance .

But it 's a giant opportunity , his unfiltered chance to make the case against change .

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Stakes for Obama 's speech are higher after two prime-time performances

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Democratic pollster : `` This convention is now a home run derby ''

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Targeting in Charlotte differs from the messaging in Denver four years ago

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Thursday night , Obama 's challenge is to sell his road map